|Sumner, Ann Louise|
Submitted to: Laboratory Publication
Publication Type: Other
Publication Acceptance Date: 9/14/2005
Publication Date: 9/14/2005
Citation: Sumner, A., Dindal, A., Willenberg, Z., Riggs, K., Pfeiffer, R.L., Hatfield, J.L., Winnegar, E. 2005. Environmental technology verification report: Horiba Instruments,Inc., APSA-360 Ambient Hydrogen Sulfide Analyzer. Laboratory Publication. Available: http://www.epa.gov/etv/centers/center/.html Interpretive Summary:
Technical Abstract: The objective of this verification test was to evaluate the APSA-360’s performance in measuring gaseous hydrogen sulfide (H2S) in ambient air at an animal feeding operation (AFO). The verification test was conducted between April 25 and June 3, 2005, at a swine finishing farm near Ames, Iowa; the APSA-360 operated at the test site from May 16 through June 3, 2005 (Weeks 4, 5, and 6 of the verification test). This site was selected to provide realistic testing conditions and was expected to exhibit a wide range of H2S concentrations during the test period. The verification test was designed to evaluate accuracy, bias, precision, linearity, span and zero drift, response time, interference effects, comparability, data completeness, and operational factors. The APSA-360 response to a series of H2S gas standards was used to evaluate accuracy, bias, precision, and linearity. The APSA-360 was factory-calibrated prior to this verification test and verified with a 400-part-perbillion (ppb) dilution from an H2S gas standard [100 parts per million (ppm) H2S] that was independent of the gas standard (5.12 ppm H2S) used for performing this verification test. All gas standard dilutions were prepared using the same dynamic dilution system. Each gas standard dilution was delivered in triplicate, and the series of gas standards was delivered twice during the verification test. Accuracy was calculated at each concentration and for each replicate relative to the nominal H2S concentration. Bias was calculated for each series of multipoint H2S challenges. Precision was demonstrated by the reproducibility of the APSA-360 response at each nominal H2S concentration. Linearity was assessed by establishing a multipoint calibration curve from the APSA-360 responses. The baseline response of the APSA-360 to zero air and a 30-ppb dilution of a compressed H2S gas standard was determined during the first day of testing, which, for the APSA-360, occurred in Week 4 of the verification test. At least twice each week, zero air and a 30-ppb H2S standard were supplied to the APSA-360 for 20 minutes for a total of 7 zero/span checks. (Results from two span checks could not be used to evaluate drift because the gas standard dilution system was not flushed before performing the span checks.) Each response was compared to the Week 4 baseline response to determine whether drift occurred in the response to zero air or the 30-ppb H2S standard. The data collected during the zero/span baseline response check were used to determine the APSA-360 response time. To determine interference effects, the APSA-360 was challenged with a series of gases (supplied at either 100 or 500 ppb in the presence and absence of 100 ppb of H2S) that may be present at an AFO and could interfere with the APSA-360 response to H2S. The comparability of the APSA-360 response to ambient air was evaluated by comparing its response to two H2S reference methods (time-integrated and in situ), which were carried out by USDA and Applied Measurement Science. The two reference methods were based on American Society for Testing and Materials Method D5504-01, with pulsed flame photometric detection substituted for sulfur chemiluminescence detection. Operational factors such as maintenance needs, data output, consumables used, ease of use, and repair requirements were evaluated based on the observations of Battelle and USDA staff. Data completeness was assessed based on the overall data return achieved by the APSA-360.